Overfertilization of surface waters and degradation of potable water sources in densely populated areas led to pollution control regulations calling for removal of nutrients in the treatment of municipal and industrial waste waters. Consequently, in the biological treatment of waste waters attention is being focused on single-sludge suspended growth system combining the processes of carbon oxidation, nitrification, denitrification and removal of phosphorus in one or more reactors without the intermediate clarification and without the addition of external carbon source for denitrification and without addition of chemicals for removal of phosphorus.
It is known, that for a high rate biological removal of carbonaceous, nitrogenous and phosphorous compounds in a single sludge system it is necessary to maintain: (a) a high concentration of mixed microbial population in the biochemical reactor, (b) an efficient contact of the mixed microbial population with the incoming waste water, (c) an efficient mixing of the partially treated waste water with the incoming waste water and with the mixed microbial population for a short period without the dissolved oxygen being present in the reactor mixed liquor and for a short period with the dissolved oxygen being present in the reactor mixed liquor, and (d) a controlled withdrawal of the excess sludge.
To comply with the above process requirements, the current treatment systems utilize biochemical reactors that require compressors and/or surface aerators for mixing and aerating the reactor mixed liquor in the aerobic reaction zones, mechanical mixers for mixing of the reactor mixed liquor in the anoxic zones, pumps for recirculating the reactor mixed liquor between individual zones and clarifiers that require sludge mixers or sludge scrapers and sludge return pumps, piping and valving etc. that make the treatment system operational, but complex and expensive and requiring considerable maintenance.
Therefore, it is the object of this invention to provide an efficient treatment system in which all of the above process requirements could be met and the biological reactions could be carried out reliably at minimum cost and at minimum consumption of energy.
More particularly, it is the object of this invention to provide a biochemical reactor that would provide and reliably maintain the conditions required for a high rate biooxidation of carbonaceous compounds, biological nitrification and denitrification and biological uptake of phosphorus in a single reactor and a single suspended growth sludge system.
It is also the object of this invention to provide a simple and maintenance free biochemical reactor with high energy utilization efficiency in mixing, recirculating and aerating of the reactor mixed liquor without the use of the traditional compressors, surface aerators, mixers and recirculation pumps, that could be constructed from concrete, steel, fiber glass and or other suitable material.
Another object of this invention is to combine the biochemical reactor with a clarifier into a simple treatment system not requiring compressors, pumps, surface aerators, mixers, piping, etc. for reliable operation, that could be easy to scale up or down for use in standardized package plants.
It is another object of this invention to provide a treatment system that would be capable to operate reliably with high concentration of powdered minerals, activated carbon, saw dust, or their mixtures present in the system.
Another object of this invention is to provide a system for biological treatment of waste waters capable of cyclic "on-off" operation to permit optimum utilization of energy at batch-wise flow conditions occuring in small package plants and particularly in single house sewage treatment systems.
Other objects and features of the invention will be understood from the accompanying drawings and the following description of claims.